MX2008001102A - Flexible absorbent article with improved body fit. - Google Patents

Abstract

An absorbent article that has a thin, conformable absorbent core where the core has at least two layers, both of which are substantially free of cellulosic fibers is described. The absorbent article has a Circular Bend Flexibility of less than about 15 N and an acquisition rate on the third gush of less than about 170 seconds and/or on the fourth gush of less than about 190 seconds.

Description

FLEXIBLE ABSORBENT ARTICLE WITH BETTER BODY ADJUSTMENT FIELD OF THE INVENTION The present invention relates to an absorbent article, preferably, to a disposable absorbent article, such as a diaper. The present invention specifically relates to an absorbent core for that absorbent article that increases the softness and fit of the article to the body of a wearer. This absorbent core is also useful to provide an absorbent article that offers greater ease of use.

BACKGROUND OF THE INVENTION Absorbent articles, such as diapers and incontinence products in adults, are well-known commercial items. Multiple attempts have been made to provide them with a good overall fit and a high absorption capacity. Modern diapers make use of superabsorbent materials that allow storing significant quantities of aqueous liquids, such as urine (eg, of the order of 300 mL in a typical baby diaper). While such an absorbent article is generally a disposable product, it is often used for many hours either dry or laden with urine. Therefore, it is very important that the article is comfortable to use when it is dry and also when it is totally or partially loaded with urine (or other bodily fluids). One of the ways in which the industry has addressed the ease of use is the provision of thinner absorbent articles. For example, U.S. Pat. no. No. 4,673,402 discloses an absorbent article with a two-ply core, wherein the lower core component has a relatively high concentration of superabsorbent material and density. U.S. Pat. no. No. 4,950,264 discloses sanitary napkins with fiber / superabsorbent material mixtures, wherein the superabsorbent is present in a relatively high concentration. U.S. Pat. no. 5,102,597 discloses absorbent polymer macrostructures comprising a crosslinked aggregate between particles, wherein each superabsorbent particle is reacted with an interparticle crosslinking agent to form an aggregate that can take the form of a canvas. U.S. Pat. no. 5,411, 497 discloses an absorbent article that includes superabsorbent material located within distinct cavities, formed between a first and a second carrier layer, and water-sensitive bonding means to secure the carrier layers together and form the cavities. The U.S. patent application no. No. 10 / 776,839 describes absorbent articles having a discontinuous layer of superabsorbent material. The layer may contain up to about 20% of an absorbent fibrous material. The industry has also considered increasing density as a means to achieve a lower thickness. For example, the published U.S. patent application. no. 2005/01 19632 describes absorbent structures which are said to have a relatively high concentration of superabsorbent material, a relatively high density and a relatively high level of flexibility. However, there is a permanent need for absorbent articles that are thinner and more flexible and that maintain the ability to capture and store a sufficient amount of the fluid deposited thereon to maintain the desirable dry state in the user's skin and offer satisfactory performance with respect to leaks. The caregivers and the adult users of those absorbent articles wish that the diaper be concealed more under the clothes or, in the case of the diapers for infants, that are more similar to the underwear. It is also desired that the cores are more adaptable in order to reduce the amount of material that is placed in the crotch area of the wearer.

BRIEF DECRIPTION OF THE INVENTION The present invention is directed to an absorbent article, preferably a disposable absorbent article., such as a diaper. The diaper has a thin and adaptable absorbent core, wherein the core structure provides improved diaper flexibility according to measurements made with a circular curve test. Conveniently, the diaper has a core region with a circular curve flexibility of less than about 15 N, and a pickup rate which in the third discharge is less than about 170 seconds or less than about 190 seconds.

BRIEF DESCRIPTION OF THE FIGURES Figure 1 is a plan view of a diaper as a preferred embodiment of an absorbent article in accordance with the present invention. Figure 2 is a cross-sectional view of the diaper illustrated in Figure 1 taken along the cut line 2-2 of Figure 1. Figure 3 is a schematic view of an apparatus for producing a preferred embodiment of the cores of the present invention.

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an absorbent article, preferably, to a disposable absorbent article, such as a diaper for children or a product for incontinence in adults. As used herein, the following terms have the following meanings: The terms "superabsorbent material", "superabsorbent polymer", "SAP", "absorbent gelling material" and "AGM" refer to a polymeric material that can absorb a amount of at least about 5 times its weight of an aqueous fluid, such as 0.9% saline, according to measurements made with the Centrifugal Holding Capacity test, as is known to those with industry experience. "Absorbent article" refers to devices that absorb and contain liquids and more specifically, refers to devices that are placed against or in proximity to the user's body to absorb and contain the liquid exudates discharged from the body. Absorbent articles include, but are not limited to, diapers, adult incontinence briefs, training pants, diaper liners and liners, sanitary napkins and the like. The term "diaper" refers to an absorbent article that is generally worn around the lower torso by infants and people suffering from incontinence. In this document, the term "disposable" is used to describe articles that are not generally intended to be washed or, in any other way, restored or reused (that is, they are intended to be disposed of after a single use and, for preference is recycled, transformed into compost or, failing that, disposed of in some other way in a way that is compatible with the environment). The terms "comprise", "comprising" and "comprise" specify the presence of what follows (eg, a component), but do not exclude the presence of other characteristics, elements, steps or components known in the industry. or described herein. A structure (eg, a layer) that is "substantially free of cellulose" means that the structure comprises at least 90% by weight of superabsorbent material and less than 10% (by weight of the structure) of cellulose fibers , generally, less than 5% cellulose fibers or less than 1% cellulose fibers or, optionally, no cellulose fiber and, generally, means that the structure comprises at least about 90% superabsorbent material . Preferably, these substantially cellulose-free structures comprise at least about 95% superabsorbent material or, in certain embodiments, at least about 99% superabsorbent material. Figure 1 is a plan view of a preferred embodiment of an absorbent article, diaper 20, in accordance with the present invention. The diaper is shown in its flat configuration and without contracting (ie, without elastic-induced contraction). The portions of the structure are cut to more clearly show the underlying structure of the diaper 20. The portion of the diaper 20 that contacts the wearer is oriented towards the observer. In Figure 1, the frame 22 of the diaper 20 comprises the main body of the diaper 20 and does not include the core 28 thereof. The frame 22 comprises an outer cover that includes a liquid-permeable top sheet 24 and a bottom sheet 26. The frame preferably also includes side panels 30., elasticized leg cuffs 32 and an elasticised waist 34, the leg cuffs 32 and the elasticized waist each generally comprise the elastic members 33. An end portion of the diaper 20 is configured as a first waist region 36 of the diaper 20. The opposite end portion is configured as a second waist region 38 of the diaper 20. An intermediate portion of the diaper 20 is configured as a crotch region 37, which extends longitudinally between the first and second waist regions 36 and 38. The waist regions 36 and 38 may include elastic elements so that they are gathered around the waist of the wearer to provide better fit and containment (eg, waist elastic member 34). The crotch region 37 is that portion of the diaper 20 which, when the diaper 20 is worn, is generally located between the user's legs. The diaper 20 is illustrated with its longitudinal axis 10 and its transverse axis 12. The periphery of the diaper 20 is defined by the outer edges of the diaper 20 in which the longitudinal edges 44, in general, are parallel to the longitudinal axis 10 of the diaper 20 , and the end edges 46 are between the longitudinal edges 44, generally parallel to the transverse axis 12 of the diaper 20. The frame also comprises a fastening system, which may include at least one fastening member 40 and at least one area for placement 42. For the unitary absorbent articles, the frame 22 comprises the main structure of the diaper with other added features to form the composite structure of the diaper. While diaper 20 can be assembled in a variety of well-known configurations, preferred diaper configurations are generally described in U.S. Pat. num. 4,940,464, 5,554,145; 5,569,234; 6,004,306, the U.S. patent application. no. of series 10/171, 249 and the U.S. patent application. no. of series 10 / 824,121. The absorbent core 28 of Figure 1 is generally located between the upper canvas 24 and the lower canvas 26. The absorbent core 28 can comprise any absorbent material that is generally compressible, conformable, does not irritate the skin of the absorbent core. user and is able to absorb and retain fluids such as urine and other certain body exudates. Exemplary absorbent structures for use as absorbent units are described in U.S. Pat. num. 4,610,678; 4,834,735; 5,260,345; 5,387,207; 5,397,316 and 5,625,222. As can be seen more clearly in Figure 2, the absorbent core 28 comprises at least two layers: the collection system 50 comprising at least the capture / storage layer 54 which, in addition to capturing the fluids, distributes and temporarily stores the fluids. captured fluids and permanently stores a part of them; and the storage system 60 which provides most of the storage capacity of the diaper 20. The upper canvas 24 is conformable, soft to the touch and does not irritate the wearer's skin. In addition, the upper sheet 24 is permeable to liquids and allows them to easily penetrate through their thickness. A suitable top sheet 24 can be manufactured from a wide range of materials, such as porous foams, cross-linked foams, perforated plastic films, natural fibers (eg, wood or cotton fibers), synthetic fibers (e.g. , polyester or polypropylene fibers), or a combination of natural and synthetic fibers. In one embodiment, the upper sheet 24 is made of a hydrophobic material to isolate the user's skin from the liquids contained in the absorbent core 10. Preferably, the upper sheet comprises a means for regulating the hydrophilicity of the material. A preferred top canvas 24 comprises a nonwoven fabric material which is made using means well known to those with experience in the textile industry. Preferably, the top sheet 24 has a basis weight of from about 10 to about 25 g / m2, a minimum resistance to dry tension of at least about 150 g / cm in the machine direction, and a penetration of less than about 3 g / cm. seconds in accordance with the standard method 150.4-99 of EDANA (European Disposables and Nonwovens Associatíon (European Association of disposable and non-woven products)). A suitable top sheet 24 comprises a non-woven propylene spunbond fabric comprising fibers of less than 3 denier with a basis weight of about 18 g / m2 and obtainable from BBA Fiberweb of Simpsonville, SC. Preferably, the lower canvas 26 is attached to the upper canvas 24 in at least a portion of the periphery thereof. The lower canvas 26 prevents the exudates absorbed by the absorbent core 28 and retained in the diaper 20 from fouling other external articles that may come into contact with the diaper 20, such as sheets and clothing. Preferably, the bottom sheet 26 is made with a thin polymeric film. In a preferred embodiment, the film comprising the lower canvas 26 is impermeable to liquids. Generally, the bottom sheet 26 comprises a layer of polyethylene film having a basis weight of about 10 g / m2 to about 30 g / m2, although other flexible liquid impervious materials may be used. Preferably, the film is vapor permeable (eg, by means of micropores) to allow the vapors to escape from the diaper 20 and also at the same time prevent the exudates from passing through the lower canvas 26. Particularly preferred are the materials of lower canvas having a non-woven fabric laminated to the film layer, such that the lower canvas 26 resembles more a cloth. A nonwoven fabric layer of this type can comprise a non-woven fabric material (e.g., one having a structure spun by bond or other suitable structure) with a basis weight of about 15 g / m2 to about 25 g / m2. Suitable materials for use as undercoat 26 can be obtained from Clopay Plástic Products Company of Mason, OH. The diaper 20 may also include other features (not shown), such as those known in the industry, including front and back ear panels, waist cap features, elastics and the like to provide better aesthetic characteristics. , of adjustment and containment. These additional features are well known in the industry and are described, for example, in U.S. Pat. no. 3,860,003 and in U.S. Pat. no. 5,151,092. In order to keep the diaper 20 placed on the user's body, at least a portion of the first waist region 36 is attached by means of the fastening member 42 to at least a portion of the second waist region 38 to form openings for the legs and an opening for the waist. The fastening system is designed to allow a user of the article to take an element of the fastening system, such as the fastening member 42, and connect the first waist region 36 with the second waist region 38 in at least two places. . This is achieved by manipulating the bonding forces between the fastener elements. Figure 2 shows a cross section of Figure 1, taken along section line 2-2 of Figure 1; starting from the body-facing side, the diaper comprises the top sheet 24, the absorbent core 28 components and the bottom sheet 26. The absorbent core 28 preferably comprises a pick-up system 50 preferably comprising a top layer. collection 52 located below the upper canvas 24, and a capture / storage layer 54 disposed between the acquisition layer 52 and the other components of the core 28, storage system 60. In particularly preferred embodiments, the core 28 is narrower in the crotch region 37 than in any of the waist regions 36, 38. Preferably, the ratio of the width of the core 28 in the transverse axis 12 to the wider lateral width thereof in the first waist region 36 or in the second Waist region 38 is less than 1.0. More preferably, the ratio is less than about 0.8, most preferably less than about 0.7. In a preferred embodiment, the acquisition layer 52 comprises a non-woven fabric. Alternatively, the capture layer 52 may comprise chemically hardened twisted and undulated fibers, foams or other materials suitable for capturing aqueous fluids as are known in the industry. As will be discussed in detail below, the capture / storage layer 54 is substantially free of cellulosic fibers and comprises a highly permeable superabsorbent material. Preferably, the capture / storage layer 54 is in direct contact with the storage system 60. Alternatively, the storage system 60 may be wrapped with a core wrapping material to arrange a layer between the storage system 60 and the layer collection / storage 54. In a preferred embodiment, the core wrapping material comprises an upper wrapping layer 56 and a lower wrapping layer 58. Regardless of what the relationship between the collection / storage layer 54 is, the storage 60 and the various arrangements of the wrapping materials, the collection / storage layer 54 and the storage system 60 must be in continuous communication. The material comprising the wrap layers 56, 58 is preferably a non-woven fabric material. A preferred material comprises a spun-bonded layer, a melt-blown layer and another spun-bonded layer (ie, an SMS material). Non-woven fabrics materials are suitably manufactured with synthetic fibers, such as polyethylene, polyester and, most preferably, polypropylene. Especially preferred are non-woven, permanently hydrophilic fabrics and especially non-woven fabrics with durable hydrophilic coatings. That hydrophilicity can be provided by treating the non-woven fabric with a surfactant. An alternative material comprises an SMMS structure or a cellulosic tissue structure. Similarly, although not shown, the acquisition / storage layer 54 may be provided with a wrapping material for coating the layer. The right materials for the upper and lower wrapping layers 56, 58 are also suitable for use as a wrapping material in the core 28 when it is desired to wrap the acquisition / storage layer 54. In a third alternative, the wrapping materials 56, 58 line both the acquisition / storage layer 54 as the storage system 60. In this embodiment, the capture / storage layer 54 and the storage system 60 are in direct face-to-face contact. Conveniently, the capture / storage layer 54 has an area of the same size, or smaller, than the storage system 60. Preferably, the acquisition / storage layer 54 is laterally centered on the storage system 60 with the same side width , but with a longitudinal extension shorter than the storage system 60. The acquisition / storage layer 54 can also be narrower than the storage system 60 while remaining centered on it. In other words, the acquisition / storage layer 54 conveniently has an area ratio with respect to the storage system 60 of 1.0. Preferably, the area ratio is less than 1.0 (e.g., less than about 0.75), more preferably, less than about 0.50. When the acquisition / storage layer 54 is shorter in the longitudinal direction than the storage system 60, it is located such that more than 50% of its longitudinal extension is forward of the transverse axis 12. This location is convenient for placing the collection / storage layer below the point where the urine is most likely to make a first contact with the diaper 20 (sometimes referred to as the "point of contact with the urine"). This location will facilitate the uptake of the fluids absorbed by the capture / storage layer 54. Also, both the capture / storage layer 54 and the storage system 60 may comprise a non-uniform distribution of the basis weight of the superabsorbent material in the direction of machine or in the direction transverse to the machine, or in both directions. The non-uniform distribution of the basis weight can be advantageously used to provide a further, localized and predetermined absorbent capacity for the diaper 20. For example, the basis weight of the superabsorbent material could be increased in the capture / storage layer 54 or in the layer of storage 60, or both, in the region of the core 28 adjacent to the "point of contact with the urine". This "profiled" distribution could also be used to provide the diaper 20 with a convenient configuration of the core 28 for a better fit to the body. For example, predetermined base weight regions of the superabsorbent could be provided to create preferential bend zones in the core and help ensure that the core 28 is bent in a predetermined manner. In alternative embodiments (not shown), the article may be preformed by the manufacturer by joining the opposite portions of the longitudinal edges 44 adjacent the end edges 46 to create a pant. The term "breeches" used herein refers to disposable garments having an opening in the waist and leg openings designed for adults or children. A brief may be placed in its position on the user by inserting the legs thereof into the leg openings and sliding the briefs in position around the user's lower torso. A pant may be preformed by any suitable technique, including, but not limited to, joining parts of the article using indexable or non-resettable joints (eg seam, weld, adhesive or cohesive bond, fastener, etc.). A brief may be preformed anywhere along the circumference of the article (eg, secured laterally, secured to the front of the waist). While the term "panties" is used herein, panties are also commonly referred to as "closed diapers," "presumed diapers," "panty-type diapers," "training pants," and "diaper pants." Suitable pants are described in U.S. Pat. num. 5,246,433; 5,569,234; 6,120,487; 6,120,489; 4,940,464; 5,092,861; 5,897,545; 5,957,908 and the published U.S. patent application. no. 2003 / 0233082A1. In additional alternative embodiments (also not shown), the capture / storage layer 54 and the storage system 60 may comprise a removable / replaceable component of an absorbent article. These removable / replaceable components allow to "renew" the absorbent article without the need to change the entire article. The acquisition / storage layer 54 and the storage system 60 are disposed below at least one fluid-permeable layer similar to the upper canvas 24. Modes having removable / replaceable components are described in more detail in one or more of the following documents: US patent applications no. of series 08 / 828,005 filed in the name of Lavon et al. on March 27, 1997 and no. of series 11/099791 filed in the name of Lavon et al. on April 4, 2005, and the published US patent applications. num. 2004/0039361, 2002/0091368, 2003/0199844, 2004/0024379, 2004/0030314. An especially preferred storage system 60 is that which is described in U.S. no. of series 10 / 776,839 previously mentioned. In summary, the layer comprises a superabsorbent material that is stabilized by a fibrous layer of thermoplastic material, preferably a thermoplastic adhesive, for immobilizing the superabsorbent material in the dry state and in the wet state. As can be seen, this structure is practically free of cellulosic fibers. An especially preferred superabsorbent material exhibits an absorption against pressure (AAP) of at least about 20 g / g and a saline flow conductivity (SFC) greater than about 30 x 10 ~ 7 (cm3.s) / g. Preferably, the AAP is greater than about 23 g / g and more preferably greater than about 25 g / g. The AAP is measured according to the method described in the TEST METHODS section below, and the SFC is measured according to the method described in U.S. Pat. no. 5, 599, 335. In order to manufacture the storage system 60, these superabsorbent materials are used with a basis weight of at least about 200 g / m2, preferably, at least about 400 g / m2, more preferably, so less approximately 600 g / m2. In addition, in order to maintain satisfactory flexibility, the basis weight is less than about 2000 g / m2. By being practically free of cellulosic fibers, the storage system 60 exhibits a higher density than that of the components of an absorbent core used in the prior industry for similar purposes. Conveniently, a storage system 60 in accordance with the present invention exhibits a density greater than about 0.4 g / cm 3. Preferably, the density is greater than about 0.5 g / cm 3, more preferably, greater than about 0.6 g / cm 3. The capture / storage layer 54 works in conjunction with the storage system 60 to more efficiently utilize the capacity of the storage system by providing temporary capillary storage of the captured fluids to allow time for the fluids to be distributed to the storage system 60. In addition , since the acquisition / storage layer 54 comprises a superabsorbent material, said layer provides at least a part of the total storage capacity of the absorbent core 28. Fundamentally, since the acquisition / storage layer 54 is intended to provide for less part of the temporary capillary storage and the distribution of the captured fluid, this layer, when it is wet, has a more open structure than the storage system 60 (that is, a greater porosity in the wet state). In general, the industry has used fibrous structures (eg, fluff cellulose mixtures) and superabsorbent material or crosslinked cellulose fibers for this purpose). However, in the dry state, the volume of these fibrous structures is considerable compared to the virtually cellulosic fiber free capture / storage layers 54 of the present invention. Superabsorbent materials suitable for use in the acquisition / storage layer 54 are described in U.S. patent applications. num. of series 10 / 950,011; 10/941, 672; 11/091, 255; and in Japanese patent JP 2004-105118, entitled "An Aqueous-Liquid-Absorbing Agent and Its Production Process" (An absorbent agent of aqueous-liquid substances and its production process), filed in the name of Nippon Shokubai Co. Ltd. on March 31, 2004.

To manufacture the capture / storage layer 54, the superabsorbent material is used with a basis weight of at least about 100 g / m2, preferably, at least about 150 g / m2, more preferably, at least about 200 g / m2. The density of the acquisition / storage layer 54 according to the present invention is greater than that of the components of an absorbent core used in the above industry for similar purposes because this layer is practically free of cellulosic fibers. Conveniently, a capture / storage layer 54 according to the present invention has a density greater than about 0.4 g / cm3. Preferably, the density is greater than about 0.5 g / cm 3, more preferably, greater than about 0.6 g / cm 3. The acquisition / storage layer 54 and the storage system 60 also work together to provide the diaper 20 with greater fit and comfort for the wearer. Specifically, a diaper 20 comprising a core 28 wherein the collection system 50 includes at least one acquisition / storage layer 54 in accordance with the present invention conveniently exhibits a low caliber and flexibility in the crotch. As will be understood, a low gauge and a flexible material produce a flexible core that is better adapted to the body of a user independently of the movements made by said user. In addition, thin / flexible diapers are less visible under the wearer's clothing and can look very similar to an undergarment. As noted above, the cores 28 in accordance with the present invention have a suitably low gauge. Conveniently, the acquisition system 50 of the present invention comprises both a capture layer 52 and a capture / storage layer 54. For a core 28 having this structure, the core size in the dry state is less than about 5 mm when is measured at the center of the acquisition layer 52. Preferably, the core size 28 is less than about 4.5 mm, more preferably less than about 4 mm, when measured at the center of the capture layer 52. structures that do not incorporate the catch layer 52 are even thinner. It should be noted that, when many of the absorbent structures of the industry describe caliper, the caliper of the absorbent structure is described in terms of a single layer instead of the assembled layers necessary to form a complete core 28 for a diaper 20. it is thought that the low caliber of a core 28 of the present invention is particularly advantageous. In other words, the low caliber of the core 28 causes the diaper 20 to have a conveniently low gauge. That is, the thickness of all the components of the diaper between the surface of the upper cloth facing the body and the surface of the lower cloth facing the garment is significantly less than the thickness of the diapers of the previous industry.

For example, in one embodiment, a diaper 20 comprising a core 28 in accordance with the present invention has a gauge in the dry state (measured 10 cm from the front edge 29 of the core 28) of less than about 5 mm. Preferably, the gauge in dry state of the diaper 20 is less than about 4.5 mm, more preferably, less than about 4 mm. The core 28 according to the present invention is also conveniently flexible to facilitate reduced volume and better fit to the body of the diaper 20. Without being limited by theory, it is thought that the combination between a thin structure as described above (as is known, stiffness increases with thickness) and a flexible bonding of the absorbent polymer particles by means of thermoplastic material (see, for example, U.S. Patent Application Publication No. 2004/0162536) contributes to provide adequate flexibility. Therefore, the core 28 can adapt more easily to the specific anatomy of a user and respond to the movements he makes with his body. As can be seen in Example 1, the flexibility of diapers from the prior industry varies widely (from 4.0 N to 70.5 N when evaluated in accordance with the circular curve flexibility test). It will be understood that flexibility is the result of many factors that are integrated into a diaper as a finished product. For example, the circular curve flexibility of the comparison diapers A and B is remarkably different, although diapers have very similar storage systems. Without being limited by the theory, it is thought that the difference of flexibility of circular curve can be attributed to the difference of the systems of catchment. Specifically, the two-layer pick-up system used in the comparative diaper A has properties that are convenient for fluid handling (eg, the two-layer pick-up system provides considerable temporary storage for urine discharges, which produces a rapid uptake). These benefits are achieved at the expense of substantially less flexibility than that of the comparative diaper B. The reference to Example 2 shows that the core designs of the present invention maintain much of the improved flexibility of the comparative core B (-12 N for a core in accordance with the present invention vs. -44 N for comparative core A) while also providing the desirable properties for fluid handling of comparative core A (pickup speed of the third discharge: -100 seconds for a core according to the present invention vs. -200 seconds for the comparative core B). Specifically, replacing the two-layer pick-up system of the Comparative Diaper A with a storage / distribution system in accordance with the present invention provides much of the fast pick-up of the two-layer system while maintaining the characteristics of lesser thickness. and flexibility in the dry state to provide much of the dry flexibility of the comparative diaper B. Conveniently, an absorbent core 28 in accordance with the present invention has a circular curve flexibility less than about 13 N, preferably, less than about 12 N and, more preferably, less than about 10 N. Analogously, an absorbent article in accordance with the present invention exhibits substantially less circular curve flexibility than that of commercially available diapers and prior industry. Conveniently, an absorbent article in accordance with the present invention exhibits a circular curve flexibility of less than about 15 N in a sample taken from the crotch region 37, forward of the lateral center line of the absorbent core 28 thereof. Preferably, the circular curve flexibility in the crotch region 37 is less than about 13.5 N, more preferably, less than about 11 N. A method for measuring the circular curve flexibility is provided in the Test Methods section included below. The absorbent cores 28 of the present invention not only exhibit the lower caliper and improved flexibility that were previously considered, but also provide convenient properties for fluid handling. With regard to absorbent articles, at least two types of properties for fluid handling must be considered: fluid capture and fluid storage capacity. An absorbent article must have good fluid-picking properties in order to rapidly transfer the aqueous fluids from the surface of the absorbent article that is oriented towards the body to minimize the free fluid that can deviate from the folds and waistbands with the consequent filtration. In the case of the present invention, the capture / storage layer 54 works in conjunction with the acquisition layer 52 (when this acquisition layer is present) to provide a hollow volume in order to contain the "discharges" of aqueous liquids. so that the storage system 60 has time to capture these fluids and store them permanently. Since the capture / storage layer 54 comprises a highly permeable superabsorbent material, the hollow volume is maintained even after the superabsorbent material comprising the capture / storage layer 54 begins to expand upon exposure to an aqueous fluid. Fluid uptake properties can be conveniently measured using the fluid uptake test described in the TEST METHODS section below. This test measures the time an absorbent article needs to capture a predefined volume of fluids that are delivered in a series of "discharges or jets". The volume and delivery speed are intended to represent the typical conditions for an absorbent article of a specific size. Depending on the size of the item, the time it takes to capture the third or fourth fluid discharge can be an important measure of pickup performance. Conveniently, an absorbent article in accordance with the present invention has a pickup rate for the third discharge of less than about 170 seconds, preferably, less than about 150 seconds, more preferably, less than about 130 seconds Particularly preferred embodiments have a pickup speed for the third discharge of less than about 100 seconds. For larger sizes, the pickup speed for a fourth discharge is also important. Conveniently, an absorbent article in accordance with the present invention has a pickup rate for a fourth discharge of less than about 190 seconds, preferably, less than about 180 seconds, more preferably, less than about 170 seconds. Specifically, a core 28 of the present invention should provide sufficient storage capacity for its operation and at the same time provide a considerably reduced dry gauge and better flexibility. It is also known that the absorbent capacity required for an absorbent article is basically defined by the intended use of that article. That is, an absorbent article for adults suffering from incontinence will have a nominal capacity greater than that of an absorbent article for an infant. Fundamentally, an absorbent core 28 in accordance with the present invention maintains the ability to store an appropriate amount of aqueous fluid to allow a reduction in core size. The capacity can be considered in several ways, for example, as a normalized capacity, this is capacity per unit area. In this method it is considered that absorbent articles designed for larger users will have a larger nominal capacity and core area to absorb the fluids deposited there. A method for the standardized capacity is provided in the U.S. patent application. no. of series 11/091, 255. Conveniently, the portion of a core 28 according to the present invention comprising the acquisition / storage layer 54 will have a normalized capacity greater than about 0.3 g / cm2. Preferably, the normalized capacity in the core portion comprising a capture / storage layer 54 is greater than about 1.0 g / cm 2, more preferably, greater than about 2.0 g / cm 2. In portions of the core 28 that do not comprise a capture / storage layer 54, the normalized capacity is lower. In the case of designs in which the majority of the capacity to capture aqueous liquids is in the crotch region 37 or in a region adjacent thereto, the normalized capacity in those areas is conveniently less than about 0.9 g / cm 2. , preferably, less than about 0.5 g / cm2, more preferably, less than about 0.2 g / cm2. In an alternative embodiment, the core 28 is designed to provide a considerable portion of the total storage in one or both waist regions 36, 38. For this embodiment, the normalized capacity of the core in one or both waist regions 36, 38 may be equal to or greater than the normalized capacity of the core in the crotch region 37. For example, the normalized capacity of the core in the waist region may be greater than about 1.0 g / cm2, even greater than about 2.0 g / cm2. For this embodiment, the area of the crotch region 37 is smaller than the area of the embodiment described above, wherein the volume of the capacity for aqueous liquids lies within or adjacent to the crotch region 37 and the layer of crust 37. collection / storage 54 may extend towards the waist regions 36, 38. As will be understood, if it is desired to calculate the total capacity of a core 28, the respective areas of a core 28, with or without the pickup layer 54, may be determine using the means known in the industry (eg, image analysis) and multiply those areas by the normalized capacity for the area in order to determine the total capacity of a core 28 of a given size. The storage system 60 can be produced suitably with the method described in the U.S. patent application. no. series 10/776, 839 mentioned above. The acquisition / storage layer 54 can be produced with a method practically the same as that used to produce the storage system 60. The main difference is that, instead of providing a non-uniform surface to supply bonding areas in which an adhesive it is contacted directly with a substrate layer, such as described in U.S. Pat. no. of series 10 / 776,839, an application drum is provided with a series of "cavities" having a shape and volume practically defined by the shape and volume desired for the capture / storage layer 54. As will be understood, the shape and The volume of these cavities can be used to provide a predefined profile of the superabsorbent material in the capture / storage layer 54 or the storage system 60, or both. This application drum is provided with a vacuum means, as described in the U.S. patent application. no. of series 10 / 776,839 mentioned above, which is suitable for attracting a substrate towards the cavity. Any nonwoven fabric suitable for use as a substrate for the storage system 60 is also suitable for use in the production of the capture / storage layer 54. In a preferred embodiment, the storage system 60 and the acquisition / storage layer 54 they are produced so that the core 28 does not have any upper wrapping layer 56 between them. A suitable process to produce this structure is illustrated in Figure 3 and considered in the following paragraphs. As can be seen in Figure 3, a precursor of the storage layer 160 can be produced by depositing a first superabsorbent material (not shown) contained in the hopper 105 on the substrate 100. As described in the patent application of US Pat. USA no. of series 10 / 776,839, a first substrate 100 is molded to the depressions (not shown) of a first application drum 110 by means of a vacuum in the first vacuum portion 1 15 so that the depressions can be filled with the first material superabsorbent as the depression passes below the first hopper 105. After the depression passes below the first hopper 105, the first superabsorbent material is stabilized with a thermoplastic polymer applied in a first spray station 120 to form the precursor storage layer 160. The precursor of the acquisition / storage layer 154 can be produced basically in the same way. The second substrate 130 is molded to a depression of the second application drum 140 before filling the depressions with a second absorbent polymer (not shown) supplied from the second hopper 135. The second superabsorbent material used to fill the depressions is stabilized with a thermoplastic polymer supplied from the second spray station 150. To form the core precursors 128, the substrate frames carrying the storage layer precursor 160 and the capture / storage layer precursor 154 are phased to achieve alignment Correctly using the methods known in the industry and combined in the grip line 180. As will be understood, the rollers comprising the grip line 180 can be provided with cavities to receive the precursors 160, 154 in order to allow the first and second substrates 100, 130 are sealed around the periphery of the precursor layer 160 and effectively coating the core precursor 128 in a wrapping material. If necessary, one or both of the rollers forming the grip line 180 can be heated to soften the thermoplastic material and facilitate the coating passage. As will be appreciated, for coating one or both of the precursors 160, 154, independent grip lines (not shown) can be provided substantially equal to the grip line 180 and a web of suitable nonwoven fabric material (not shown).

Test methods Fluid uptake The fluid uptake test is useful for measuring the ability of an absorbent structure to quickly capture fluids under simulated use conditions. The sample is loaded with a 0.9% saline jet with a predetermined velocity and volume using a pump (the Model 7520-00 pump, distributed by Cole Parmer Instruments Co. of Chicago, IL, is suitable). The time needed to absorb the saline solution is recorded with a timer. The jet is repeated at 5 minute intervals for 4 jets. The description below is aimed at diapers for children; for other types of absorbent articles, the jet volume and confining pressure can be regulated as described herein. The test sample, which comprises a core and includes a top canvas and a bottom sheet, is arranged to be extended and flat on a foam pad inside a polymethyl methacrylate box (eg, PERSPEX methyl acrylate) (see detailed assembly of the test apparatus in U.S. Patent No. 6,083,210) and a representative weight of a typical confining pressure is placed on a methyl acrylate shell, as described below. Following are the appropriate configuration parameters for various sizes of infant diapers. If the size of the diaper to be tested is not indicated in the list, the product size is defined by determining the weight interval that has the greatest overlap with the weight ranges indicated below.

Size Approximate Weight Volume of Weight Speed for the child's pressure load confinement load (kg) (mL) (ml / s) (kg) Newborn < 4 16 5.33 0.9 at each end of the plate = 1.8 in total 1 4-6 24 8 2.3 at each end of the plate = 4.6 in total 2 5-8 40 8 2.9 at each end of the plate = 5.8 in total 3 7 -13 50 10 4.5 at each end of the plate = 9.0 in total 4 10-17 75 15 9.1 at each end of the plate = 18.2 in total 5 and larger > 12 75 15 9.1 at each end of the plate = 18.2 in total When evaluating products with capabilities significantly different from those indicated in the previous table (such as those that can be anticipated in incontinence products in adults or diapers for premature babies), the volume of fluid per jet must be adjusted to 20% of the total nominal capacity of the article, and the weight of the confining pressure must be regulated to represent the pressure exerted by a user when sitting on the product. The nominal capacity can be determined by adding the capacity of the superabsorbent material (defined as the Centrifugal holding capacity) and any contribution of fibrous material in the core (eg, 4 g / g for cellulose fibers). Any deviation from the usual test protocol should be recorded. The outer surface of the lower canvas faces the foam platform. In the upper part of the sample is placed a plate of METHYL ACRYLATE that has an opening of 5 cm in diameter practically in the middle. The sample is oriented so that the upper canvas is directly below the opening of the METHYL ACRYLATE plate. The plate opening (i.e., the loading point of the saline solution) is positioned approximately 10 cm from the front edge of the complete core and approximately midway between the lateral sides of the core. The saline solution is introduced into the sample through the cylinder placed and stuck in the opening. The electrodes are located at a distance of approximately 1 mm to 2 mm above the surface of the absorbent structure and are also connected to the timer. Loads are placed on top of the plate to simulate, for example, the weight of a baby. Two weights with an area of 744.6 cm2 (51 cm x 14.6 cm) appropriate for the specific size are placed on top of the plate (see the previous table). As the saline solution is introduced into the cylinder, it accumulates on top of the absorbent structure to complete an electrical circuit between the electrodes. This activates the timer. The timer stops and the data is recorded when the absorbent structure has absorbed the jet, and when the electrical contact between the electrodes is interrupted. The pickup speed is defined as the time in seconds necessary to absorb the volume of the jet supplied. The collection speed is calculated for each jet introduced into the sample.

Base Weight The standard method of the European Disposables And Nonwovens Association (EDANA) (European Association of disposable and non-woven products) for the mass per unit area (40.3-90) is adequate.

Caliber The standard method of the European Disposables And Nonwovens Association (EDANA) for the thickness (No. 30.5-99) is adequate. A suitable apparatus is the one described in paragraph 4.1. The specified pressure is 2.1 kPa.

Density The base weight, determined by the Base Weight Method, is divided by the caliber determined by the Method to determine the caliber.

Flexibility of circular curve Sample Preparation This method is suitable for measuring the flexibility of absorbent articles or components of the absorbent article having a core with sufficient area to be able to cut a 6.4 cm X 6.4 cm (2.5 X 6.5 inches) sample. The samples should be equilibrated at 23 ° C ± 2 ° C and 50% ± 2% relative humidity for at least two hours before the test. The side seals are opened if the absorbent article is a brief-type diaper. All elastics (leg cuffs, waistbands, etc.) of the absorbent article are removed. The absorbent article is carefully stretched on a flat surface, with the bottom sheet facing that surface, to eliminate any crease in it. The crossing of the longitudinal and transverse axes of the absorbent core is marked. 62 mm are measured along the longitudinal axis towards the front waist edge of the absorbent article and a second mark is made. With a hydraulic press (suitable presses can be obtained from Carver, Inc. of Wabash, IN) with a square die of 6.4 cm (2.5 inches), a sample centered on the second mark is cut.

Apparatus and method The circular curve method is performed on a tensile test instrument with a constant extension rate and a computer interface (a suitable instrument is the MTS Q test device used by the Testworks 4 program, which can be obtained from MTS Systems Corp, Eden Prairie, MN) and a 100 N load cell. The instrument is configured for a standard compression test using the plunger and platform accessories described in ASTM D4032-94.

(Standard test method to determine the stiffness of a fabric using the circular curve procedure). The sample is centered on the platform above the opening. The plunger is rigidly connected to the crosshead of the tensile test instrument, centered on the opening and located 20 mm above the upper plane of the platform at the beginning of the test. At the start of the test, the movement of the crosshead causes the plunger to descend at a speed of 100 mm / minute to a depth of 15 mm below the upper plane of the platform.

Repetitions and calculations At least 5 repetitions are evaluated for each sample. The circular curve flexibility is reported as the maximum peak force expressed in newtons (N). Each set of five identical replicates (or n repetitions if n is greater than 5) is tested and the five values measured for that set are averaged as the sample value. Examples Example 1 This example is intended to demonstrate the flexibility of the diaper core region of the prior machine-made industry. In this example, commercially available diapers and other diapers were evaluated in accordance with the prior industry to determine the circular curve flexibility in two sections of the crotch region (before and after the lateral centerline of the core) using the method described herein. The results of this evaluation are indicated in Table 1.

Table 1 Flexibility of circular curve in the part Type of crotch front diaper (N) Pampers Easy Ups®1 3T / 4T 51.3 Pampers Feel n Learn®1 24.4 Huggies Puli Ups®2 for girls Size 2T / 3T 18.4 Size 3T / 4T 24.7 Size 4T / 5T 15.6 Huggies Puli Ups®2 size 4 for children 49.3 Pampers Cruisers®1 Size 4 43.9 Huggies Supreme®2 Size 4 70.5 Huggies Baby Shape®2 Size 4 38.2 Comparative diaper A3 50.1 Comparative diaper B4 4.0 Cloth underwear5 0.2 1. Marketed by Procter & Gamble of Cincinnati, OH 2. Marketed by Kimberly Clark of Neenah, Wl 3. Storage system in accordance with the published U.S. patent application. no. 2004/0162536, with two-layer collection system comprising cross-linked cellulose fibers (250 g / m) and resin-bonded polyester non-woven fabric (60 g / m2) 4. Storage system in accordance with the application of US published patent no. 2004/0162536 with non-woven fabric acquisition layer comprising resin-bonded / carded polyester non-woven fabric (43 g / m2) 5. Hanes Her Way® cotton trusses, size 4, marketed by Hanes Company, Inc. of Winston-Salem, NC, two sheets of cloth in the crotch region. Due to the high flexibility, a 10 N load cell was used in the force measurement instead of a 100 N load cell.

As can be seen, the flexibility of diapers under test varies widely, and underwear is the most flexible product of all the products included in the test.

Example 2 This example is intended to compare the flexibility and the pick-up speed of the absorbent cores according to the present invention with two cores from the previous industry. In this example, core samples are disposed on a bottom sheet comprising a laminate of a spun polypropylene by bonding 18 g / m2 of BBA Fiberweb from Simpsonville, SC, and a 28 g / m2 polyethylene film of Clopay Plástic Products Company of Mason, OH, with a superior canvas (propylene spun bond by joining 18 g / m2 of BBA Fiberweb of Simpsonville, SC) arranged on them and the flexibility of circular curve in the frontal portion of the crotch region was evaluated (before the lateral center line of the nucleus) and the capture velocity for the third discharge.

Table 2 Flexibility of the average circular curve in the front part of the Pick-up speed for Crotch diaper type 3. Discharge (N) (seconds) Comparative core A1 44 90 Comparative core B2 2 198: I read according to the 12 97 present invention3 1. Storage system in accordance with the published U.S. patent application. no. 2004/0162536 (800 g / m2) with two-layer capture system comprising cross-linked cellulose fibers (250 g / m) and resin-bonded non-woven polyester fabric (60 g / m2) 2. Storage system in accordance with the nonwoven fabric acquisition layer (400 g / m2) of the published U.S. patent application. no. 2004/0162536, comprising resin bonded / carded polyester nonwoven fabric (43 g / m2) 3. Storage system in accordance with the published U.S. patent application Ser. no. 2004/0162536 (680 g / m2), collection / storage layer according to the present invention (superabsorbent material in accordance with U.S. Patent Application Serial No. 11/091, 255 with a basis weight 200 g / m2) and non-woven polyester fabric bonded with resin / carded (60 g / m2) EXAMPLE 3 This example is intended to compare the dry state gauge of the diapers in accordance with the present invention with the commercially available diapers and a diaper manufactured in accordance with the published U.S. patent application Ser. no. 2004/0162536. This comparison is shown in Table 3.

Table 3 Product Caliber in dry state (mm) Pampers® Active Fit (size 4) 1 7.1 Huggies® Super-Flex (size 4) 2 7.2 Huggies®Pull-Ups®Girl®3 3.2 HuggiesTPull-UpsTBoy®5 4.0 Diaper in compliance with the US published patent application no. 2004/01625364 5 9 Invention of this document5 3.9 1. Marketed by Procter & Gamble GMBH of Schwalbach am Tanus, Germany 2. Marketed by Kimberly Clark of Reigate, United Kingdom 3. Marketed by Kimberly Clark de Neenah, Wl 4. Two-layer capture system: comprises curly cellulose fiber (200 g / m2) and cloth non-woven polyester bonded with resin / carded (60 g / m2) 5. Collection / storage layer in accordance with the present invention The description of all patents, patent applications (and any patents granted based thereon, as well as any corresponding published foreign patent applications) and the publications mentioned throughout this description are incorporated herein by reference. reference. However, it is expressly denied that any of the documents incorporated herein by reference teach or describe the present invention. All documents cited in the Detailed Description of the invention are incorporated, in the pertinent part, by reference herein; The citation of any document should not be construed as an admission that it is a prior industry with respect to the present invention. Even when the particular embodiments of the present invention have been illustrated and described.It will be clear to those with experience in the industry that various changes and modifications can be made without departing from the spirit and scope of the invention. It will also be apparent to the skilled artisan that all combinations of the modalities and features shown in the foregoing discussion are possible and may result in preferred embodiments of the invention. It has been intended, therefore, to encompass in the appended claims all those changes and modifications that are within the scope of this invention.

Claims (4)

1. An absorbent article comprising: a) a fluid-permeable top sheet; b) a lower canvas; the lower canvas is attached to the upper canvas around a periphery of the absorbent article; and c) a core disposed between the upper canvas and the lower canvas; The core comprises: i) a storage system comprising at least one storage layer having a density of at least 0.4 g / cm3; and ii) a cellulose-free uptake system comprising a capture / storage layer with a density of at least 0.4 g / cm 3 and comprising a superabsorbent material, characterized in that the absorbent article exhibits a lower circular curve flexibility of 15 N in a region of the crotch of this one.

2. The absorbent article according to claim 1, further characterized in that it has a pickup speed of less than 170 seconds in a third discharge.

3. The absorbent article according to any of the preceding claims, further characterized in that it has a pickup speed of less than 190 seconds in a fourth discharge.

4. The absorbent article according to any of the preceding claims, further characterized in that it has a caliper of less than 5 mm in the dry state.